Alzheimer's disease (AD) research has traditionally focused on amyloid fibrils found in plaque deposits in the brain, but recent evidence suggests that oligomers of Alzheimer's beta-amyloid peptides play a more significant role in initiating AD pathology. The long-term objective of this project is, through characterizing Abeta oligomer structures, answer fundamental questions about pathways of A beta self-assembly and how these pathways could be controlled as strategies for designing therapeutics. The proposed research addresses major challenges related to oligomer stability and structural homogeneity, which have hindered oligomer structural characterization to date. We will determine the structure of a 150 kDa Abeta (1-42) oligomer by integrating solid state nuclear magnetic resonance (ssNMR) spectroscopy with computational modeling. Specifically, we will 1) define secondary structure and sidechain proximity across the amino acid sequence; 2) Determine alignments between neighboring beta -strands and conformations of non- beta -strand regions; and 3) Model the structure of the Abeta (1-42) oligomer based on the ssNMR data. The structural information obtained in this project will help characterize early events in Abeta self-assembly and may lead to diagnostic tools for early detection of Alzheimer's disease and therapeutic strategies that exploit differences in oligomer and fibril assembly pathways.